Bcl-2-associated X protein

BCL2-associated X protein
Based on PDB id 1F16
Available structures: 1f16
Identifiers
Symbol(s)	BAX; Bax zeta
External IDs	OMIM: 600040 MGI: 99702 Homologene: 7242
Gene ontology Molecular Function: • molecular_function • protein binding • BH3 domain binding Cellular Component: • cellular_component • soluble fraction • cytoplasm • mitochondrion • mitochondrial outer membrane • membrane • integral to membrane • cytosolic part Biological Process: • release of cytochrome c from mitochondria • protein insertion into mitochondrial membrane during induction of apoptosis • apoptosis • induction of apoptosis • response to DNA damage stimulus • cell cycle • germ cell development • spermatogenesis • nervous system development • induction of apoptosis by extracellular signals • induction of apoptosis by intracellular signals • negative regulation of survival gene product activity • caspase activation via cytochrome c • apoptotic mitochondrial changes • response to wounding • nuclear fragmentation during apoptosis • regulation of apoptosis • regulation of caspase activity • negative regulation of progression through cell cycle • retinal cell programmed cell death • negative regulation of fibroblast proliferation • protein homooligomerization
RNA expression pattern
More reference expression data
Orthologs
	Human	Mouse
Entrez	581	12028
Ensembl	ENSG00000087088	ENSMUSG00000003873
Uniprot	Q07814	Q3TXJ7
Refseq	NM_004324 (mRNA) NP_004315 (protein)	NM_007527 (mRNA) NP_031553 (protein)
Location	Chr 19: 54.15 - 54.16 Mb	Chr 7: 45.33 - 45.33 Mb
Pubmed search	[1]	[2]

The Bcl-2–associated X protein, or BAX, gene was the first identified pro-apoptotic member of the Bcl-2 protein family. Bcl-2 family members share one or more of the four characteristic domains of homology entitled the Bcl-2 homology (BH) domains (named BH1, BH2, BH3 and BH4), and can form hetero- or homodimers. Bcl-2 proteins act as anti- or pro-apoptotic regulators that are involved in a wide variety of cellular activities.

Bax is a pro-apoptotic Bcl-2 protein containing BH1, BH2 and BH3 domains. In healthy mammalian cells, the majority of Bax is found in the cytosol, but upon initiation of apoptotic signaling, Bax undergoes a conformation shift, and inserts into organelle membranes, primarily the outer mitochondrial membrane. Bax is believed to interact with, and induce the opening of the mitochondrial voltage-dependent anion channel, VDAC. Alternatively, growing evidence suggest that activated Bax and/or Bak form an oligomeric pore, MAC in the outer membrane. This results in the the release of cytochrome c and other pro-apoptotic factors from the mitochondria, often referred to as mitochondrial outer membrane permeabilization, leading to activation of caspases. This defines a direct role for Bax in mitochondrial outer membrane permeabilization, a role common to the Bcl-2 proteins containing the BH1, BH2 and BH3 domains.

The expression of BAX is upregulated by the tumor suppressor protein p53, and Bax has been shown to be involved in p53-mediated apoptosis. The p53 protein is a transcription factor that, when activated as part of the cell's response to stress, regulates many downstream target genes, including BAX. However, p53 also has a transcription-independent role in apoptosis. In particular, p53 interacts with Bax, promoting Bax activation and the insertion of Bax into the mitochondrial membrane.

See also

• Apoptosis
• Apoptosome
• Bcl-2
• BH3 interacting domain death agonist (BID)
• Caspases
• Cytochrome c
• Noxa
• Mitochondrion
• p53 upregulated modulator of apoptosis (PUMA)

Further reading

• Vieira HL, Haouzi D, El Hamel C, et al. (2001). "Permeabilization of the mitochondrial inner membrane during apoptosis: impact of the adenine nucleotide translocator.". Cell Death Differ. 7 (12): 1146-54. doi:10.1038/sj.cdd.4400778. PMID 11175251.
• Buytaert E, Callewaert G, Vandenheede JR, Agostinis P (2007). "Deficiency in apoptotic effectors Bax and Bak reveals an autophagic cell death pathway initiated by photodamage to the endoplasmic reticulum.". Autophagy 2 (3): 238-40. PMID 16874066.
• Steele AD, Yi CH (2007). "Neuromuscular denervation: Bax up against the wall in amyotrophic lateral sclerosis.". J. Neurosci. 26 (50): 12849-51. PMID 17171827.